Reconfigurable optical networks

ABSTRACT

A system, e.g. a reconfigurable optical channel router, includes an input waveguide optically connected to a wavelength demultiplexer. A first input microcavity resonator set including a plurality of microcavity resonators is located adjacent the input waveguide. The microcavity resonators are configured to controllably couple to a corresponding one of a plurality of frequency channels of an optical signal propagating within said input waveguide.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No. 13/538,525 (the '525 Application) filed on Jun. 29, 2012 and incorporated by reference herein. This application is further related to U.S. patent application Ser. No. 13/800,403 (the “'403 Application”) filed on even date herewith and incorporated by reference herein. The present application claims the benefit to the previously filed U.S. Provisional Patent Application No. 61/667,374 also of the same title, filed Jul. 2, 2012, and which is incorporated herein by reference in its entirety. The present application further claims the benefit to the previously filed U.S. Provisional Patent Application No. 61/667,380 (the '380 Application) of the same title, filed Jul. 2, 2012, and which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This application is directed, in general, to optical communications systems and methods.

BACKGROUND

This section introduces aspects that may be helpful to facilitating a better understanding of the inventions. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.

Optical switching networks employ a switching topology that may be referred to as an “optical switch fabric.” As the size and speed of such networks grows, new optical switch fabrics that provide greater capability are needed to keep pace with such growth. One aspect of capability to be addressed is configuration of such optical networks.

BRIEF SUMMARY OF ILLUSTRATIVE EMBODIMENTS

One aspect provides a system, e.g. a reconfigurable optical channel router. The system includes an input waveguide optically connected to a wavelength demultiplexer and configured to propagate a plurality of wavelength channels of an optical carrier signal. A first input microcavity resonator set is located adjacent the input waveguide. The set includes a plurality of microcavity resonators that are each configured to controllably couple to a corresponding one of a plurality of frequency channels of an optical signal propagating within the input waveguide.

Another aspect provides a method, e.g. for forming an optical system, e.g. a reconfigurable optical channel router. The method includes forming an input waveguide optically connected to a wavelength demultiplexer. Microcavity resonators of a first input set of microcavity resonators are formed located adjacent the input waveguide. Each microcavity resonator is configured to controllably couple to a corresponding one of a plurality of frequency channels propagating within the input waveguide.

Yet another aspect provides a method, e.g. for forming an optical system, e.g. a reconfigurable optical router. In a first step of the method a first substrate is provided. The first substrate has an input waveguide optically connected to a wavelength demultiplexer. A first input microcavity resonator set including a plurality of microcavity resonators located adjacent the input waveguide. The microcavity resonator set includes a plurality of microcavity resonators, each being configured to couple to a different frequency channel of an optical signal propagating within the input waveguide. In a second step of the method a second substrate is provided. The second substrate has an electronic controller formed thereover. The controller is configured to control each of the microcavity resonators to controllably couple to a corresponding one of the frequency channels. In a third step of the method the first and second substrates are joined, thereby operably connecting the controller to the microcavity resonators.

In any embodiment a plurality of output waveguides may be formed, each waveguide being optically connected to the wavelength demultiplexer. In such embodiments the wavelength demultiplexer may be configured to route each carrier signal to a corresponding one of the output waveguides. Any embodiment may include forming a plurality of output microcavity resonator sets. Each resonator set includes a corresponding plurality of microcavity resonators. Each microcavity resonator of each output set is located adjacent a same corresponding one of the output waveguides such that the microcavity resonators of each output set may controllably couple to a corresponding different wavelength channel propagating within the corresponding output waveguide.

In some such embodiments a plurality of optoelectric transducers may be formed, with each of the transducers being optically coupled to a corresponding one of the output microcavity resonators. Each transducer is configured to convert an optical signal within its corresponding resonator to an electrical signal.

In any embodiment the wavelength demultiplexer may include an arrayed waveguide grating (AWG). In any embodiment the AWG may be configured to provide cyclic permutations of optical paths of the wavelength channels between inputs and outputs of the AWG. In any embodiment the waveguide and wavelength demultiplexer may be formed from silicon. Any embodiment may include control electronics configured to modulate a resonant frequency of the microcavity resonators. In any embodiment the microcavity resonators may be ring resonators.

One embodiment is a system comprising a first plurality of separate sets of optical ring resonators, a second plurality of separate sets of optical ring resonators, and an optical multiplexer/demultiplexer. The optical multiplexer/demultiplexer has a set of optical inputs and a set of optical outputs. Each set of the first plurality of separate sets is optically connected to a corresponding one of the optical inputs of the optical multiplexer/demultiplexer. Each set of the second plurality of separate sets is optically connected to a corresponding one of the optical outputs of the optical multiplexer/demultiplexer.

Some such embodiments further comprise a plurality of first devices, each first device being connected to modulate digital data streams onto optical carriers via the ring resonators of a corresponding one of the sets of the first plurality. Some such embodiments further comprise a plurality of first apparatuses, each first apparatus being connected to demodulate digital data streams from optical carriers via the ring resonators of a corresponding one of the sets of the second plurality. Some such embodiments further comprise a plurality of first apparatuses, each first apparatus being connected to demodulate digital data streams from optical carriers via the ring resonators of a corresponding one of the sets of the second plurality. Some such embodiments further comprise an electronic controller capable of separately adjusting resonant frequencies of some of the ring resonators of the sets of the first plurality. Some such embodiments further comprise a plurality of first optical fibers, each first optical fiber connecting a corresponding one of the sets of the first plurality to a multi-wavelength channel optical source. In some such embodiments each first optical fiber connects to a corresponding one of the optical inputs of the optical multiplexer/demultiplexer.

BRIEF DESCRIPTION OF DRAWINGS

Reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a system, e.g. an M×N reconfigurable optical network according to one embodiment, that provides optical domain switching of received wavelength channels of wavelength division multiplexed (WDM) signals;

FIG. 1A schematically illustrates operation of the optical network of FIG. 1 in a nonlimiting embodiments to optically provide data connections between input electrical devices and output electrical devices;

FIG. 2 illustrates aspects of a frequency comb including a number of wavelength channels;

FIG. 3 illustrates an opto-electric domain converter used in various embodiments to convert a modulated optical signal to the electrical domain;

FIG. 4A illustrates a signal routing in one illustrative embodiment by an arrayed waveguide grating that may be used in a switching stage of the system of FIG. 1;

FIG. 4B illustrates another signal routing in one illustrative embodiment by an arrayed waveguide grating that may be used in a switching stage of the system of FIG. 1;

FIG. 4C illustrates another signal routing in one illustrative embodiment by an arrayed waveguide grating that may be used in a switching stage of the system of FIG. 1;

FIG. 5A illustrates an embodiment in which portions of the system are formed on separate substrates that are joined to form the system, e.g. the system of FIG. 1;

FIG. 5B illustrates another embodiment in which portions of the system are formed on separate substrates that are joined to form the system, e.g. the system of FIG. 1;

FIG. 5C illustrates another embodiment in which portions of the system are formed on separate substrates that are joined to form the system, e.g. the system of FIG. 1; and

FIG. 6 presents a flow diagram of a method, e.g. for forming a system, e.g. the system of FIG. 1, according to various embodiments; and

FIG. 7 presents a flow diagram of a method, e.g. for forming a system, e.g. the system of FIG. 1, according to various embodiments.

DETAILED DESCRIPTION

The inventors believe that a compact and flexible architecture for switching data in an optical network may be implemented using microcavity resonators coupled to waveguides to, e.g. selectively add and drop modulated optical signals within an opto-electric switching matrix. Embodiments may be used to provide compact and low-cost signal routing at a small scale, e.g. within a photonic integrated circuit, a medium scale, e.g. within a data center, or large-scale, e.g. long-haul optical communication system.

Some structures and/or methods described in '380 Application, and/or the '403 Application, may be suitable for making or using similar structures and/or methods of the present application.

FIG. 1 presents a system 100, e.g. an embodiment of an MN×NM reconfigurable electrical cross-connect 100. The cross-connect 100 uses optical wavelength channels to selectively route digital data signal streams between M electrical ports of N output devices to N ports of M input devices in a one-to-one manner with respect to individual ports of the input and output devices. The individual input ports are indexed by a pair of integers (m, n), i.e., m=1, 2, . . . M and n=1, 2, . . . N, and the individual output ports are indexed by a pair of integers (n, m), i.e., n=1, 2, . . . N and m=1, 2, . . . M. The parameter N describes a number of wavelength division multiplexed (WDM) carriers available to transmit data. The system 100 includes three principal sections that are described in turn, a location-distributed transmitter stage 105, a passive switching stage 110, and a location-distributed receiver stage 115. The system 100 is configurable to support different values of M and N. Accordingly a generalized architecture is used to describe the system 100, with more specific examples being used to describe some detailed aspects of the system 100.

The transmit stage 105 includes N optical power waveguides 120-1, 120-2 . . . 120-N, collectively referred to as waveguides 120. The transmit stage 105 further includes N input microcavity resonator sets 125-1, 125-2 . . . 125-N, wherein each set is optically coupled to a corresponding one of the optical power waveguides 120-1, 120-2 to 120-N. Each of the microcavity resonator sets 125-1 to 125-N includes M microcavity resonators 130, as further described below. Each microcavity resonator set 125 may include, e.g. an optical ring resonator (microring) or an optical disk resonator (microdisk) reconfigurably configured to resonate at an optical wavelength, e.g. in the S band (1460 nm-1530 nm), the C band (1530 nm-1565 nm) or the L band (1565 nm-1625 nm). The remaining discussion refers to the microcavity resonators as ring resonators without limitation thereto. The microcavity resonator sets 125 may therefore also be referred to as ring resonators sets 125.

Each of the N waveguides 120-1 to 120-N receives an unmodulated, multi-channel, optical signal 200 (see FIG. 2) that is a superposition of unmodulated wavelength components. FIG. 2 schematically illustrates the spectrum of a representative unmodulated, multi-channel, optical signal 200 that includes six equally spaced, wavelength components λ₁, . . . λ₆. The individual wavelengths may be spaced by a WDM grid, frequency spacing Δf (or equivalent wavelength spacing Δλ), e.g. a regular, about even spacing of the wavelength components by a same frequency difference, e.g. about 100 GHz. Six wavelength components are shown, but embodiments are not limited to any particular number of wavelength components.

Returning to FIG. 1, and considering the ring resonator set 125-1 as an example, this set includes M ring resonators 130-11, 130-21 . . . 130-M1. Each of the ring resonators 130-11, 130-21 . . . 130-M1 may be controlled to operate with a resonant wavelength approximately equal to one of the center wavelengths, i.e., λ₁, λ₂, . . . λ_(M), of the M wavelength components of the unmodulated, multi-channel, optical signal 200.

In the transmitter stage 105, each of the ring resonators 130-11, 130-21 . . . 130-M1 is optically coupled to the optical power waveguide 120-1 such that a wavelength component of an optical signal having a wavelength near the resonant wavelength of a particular k-th ring resonator 130-1k couples to that ring resonator. A controller 135 may provide a quasi-static control signal that sets a nominal resonant frequency of a unique one of the ring resonators 130-11, 130-21 . . . 130-M1 to one of the wavelength components. The nominal resonant frequency may be changed by electro-optic, thermal or free-carrier modulation of the optical path lengths of the resonators 130. A data modulator (not shown) may modulate the resonant frequency of the ring resonators 130 to impart data on the coupled signal, e.g. by binary phase shift keying or on-off keying. For example, the resonant frequency of each resonator 130 may be rapidly switched between two resonant frequencies offset by a small amount from the nominal resonant frequency. Additional suitable examples of such modulation may be described in the '525 Application. Thus the controller 135 may operate to map the data stream delivered to each ring resonator 130 to a particular wavelength channel.

The wavelength components λ₁ . . . λ_(M) propagating within each waveguide 120 may be modulated independently. Thus, the transmitter stage can produce M×N independently data-modulated optical carriers. At outputs of the waveguides 120-1 . . . 120-N each optical signal may have any one of the wavelengths λ₁ . . . λ_(M).

In the switching stage 110, a wavelength demultiplexer 145 includes input ports 150-1 . . . 150-N and output ports 155-1 . . . 155-M. At the input ports 150, the wavelength demultiplexer 145 receives the modulated optical signals from the waveguides 120 via corresponding optical paths 140-1 . . . 140-N. While in the illustrated embodiments the optical paths 140 are shown as being physically located between the transmit stage 105 and the switching stage 110, in other embodiments segments of the optical paths 140 may be physically located between the switching stage 110 and the receiver stage 115. The optical paths 140 may include, e.g., segments of single mode optical fibers of various lengths. Short path lengths may be used in embodiments for which the system 100 is implemented as, e.g., an integrated photonic optical processor. Long path lengths may be used in embodiments for which the system 100 is implemented as, e.g., in a long-haul communication system. A medium path length may be used in embodiments for which the system 100 is implemented as, e.g., a communication network inside of a data processing center.

In various embodiments, the wavelength demultiplexer 145 demultiplexes the wavelength components of the optical carrier signals received at each input port 150 and routes these components to the output ports 155 in a wavelength-selective manner. For example, the wavelength demultiplexer 145 may route each one of the M wavelength components received from the waveguide 120-1 to a corresponding one of the M output ports 155.

In various embodiments, the wavelength demultiplexer 145 typically routes the individual wavelength components of a WDM optical signal in a sequential and cyclic fashion to the output ports 155. For example, if the input 150-1 receives a WDM optical signal with M wavelength components in a wavelength-sequential sequence λ₁, λ₂, λ₃ . . . λ_(M), these components may be routed to the output ports 155 such that a k-th wavelength λ_(k) is output at the first output 155-1, a next cyclically sequential wavelength λ_(k+1) is output at the second output 155-2, and so on such that the wavelength λ_((k+M−1)) is output at the M-th output 155-M. Here, {k+M−1} designates the integer equal to k+M−1 modulo M and located in the interval [1, M].

Thus, the demultiplexer 145 may be any conventional wavelength-cyclic optical demultiplexer, e.g., an AWG-based optical demultiplexer. Herein, such a demultiplexer may be referred to as a cyclic optical demultiplexer.

FIGS. 4A-4D illustrate without limitation the ordering of channel frequencies at the outputs of the wavelength demultiplexer 145 in a more specific embodiment. In the following discussion, for example and without limitation, N and M are each taken to be 4, and the wavelength demultiplexer 145 implements cyclic permutations of wavelength components. The center wavelength of each wavelength channel is described as λ_(M). In FIG. 4A, wavelength components λ₁, λ₂, λ₃, and λ₄ received at the input port 150-1 are wavelength-selectively routed by the wavelength demultiplexer 145 to the output ports 155-1, 155-2, 155-3, and 155-4, respectively. In FIG. 4B, wavelength components λ₁, λ₂, λ₃, and λ₄ received at the input port 150-2 are wavelength-selectively routed by the wavelength demultiplexer 145 to output ports 155-4, 155-1, 155-2 and 155-3, respectively. In FIG. 4C, wavelength components λ₁, λ₂, λ₃, and λ₄ received at the input port 150-3 are wavelength-selectively routed by the wavelength demultiplexer 145 to output ports 155-3, 155-4, 155-1, and 155-2, respectively. In FIG. 4D, wavelength components λ₁, λ₂, λ₃, and λ₄ received at the input port 150-4 are wavelength-selectively routed by the wavelength demultiplexer 145 to output ports 155-2, 155-3, 155-4 and 155-1, respectively.

The wavelength demultiplexer 145 is not limited to any particular implementation. Some convenient implementations include an arrayed waveguide grating (AWG) based optical cross-connect. As known to those skilled in the optical arts, an AWG based optical cross-connect may be used to route a sequence of wavelength components of a WDM optical signal to a parallel, spatial sequence of optical outputs in a wavelength-selective manner. As already mentioned, an AWG based wavelength selective cross-connect may also route wavelength channels in a manner that is cyclic in the sequence of components to the outputs. Moreover, an AWG-based device may be implemented in a planar waveguide process, e.g. silica on an SOI substrate, thereby being well suited to integration in a photonic integrated circuit (PIC).

Embodiments of the wavelength demultiplexer 145 are not limited to implementation with an AWG. For example, a cyclic wavelength demultiplexer may be also based on an Echelle grating. Such a grating directs substantial amounts of received light into multiple diffraction orders so that each of the M optical outputs of device 145 may be connected to receive light from multiple orders. In some alternate embodiments, the switching stage 110 may be implemented using an electronically-controlled switching matrix. For example, 2×2 electro-optic switches may be configured to implement an M×N matrix, with the switches being electronically controlled. Skilled practitioners of the optical arts are familiar with such switching matrixes. However, the size of such matrixes may grow rapidly with N making such embodiments cumbersome and expensive as N becomes large.

Returning to FIG. 1, the receiver stage 115 includes a plurality of waveguides 160, e.g. one waveguide 160-1, 160-2 . . . 160-M optically connected to a corresponding one of the output ports 155 of the wavelength demultiplexer 145. Each waveguide 160 is associated with an output ring resonator set 165. Thus, for example, the waveguide 160-1 is associated with an output ring resonator set 165-1, the waveguide 160-2 is associated with an output ring resonator set 165-2, and so on. The ring resonator set 165-1 includes N ring resonators 170-11 . . . 170-N1, e.g. one ring resonator corresponding to each of the ring resonator sets 125.

Each ring resonator 170-11 . . . 170-N1 may be configured to selectively couple to light propagating within the waveguide 160-1 at one of the channel wavelengths λ₁-λ_(M). Thus, e.g. the ring resonator 170-11 may be coupled to light propagating at the ring resonator 170-21 may be coupled to light propagating at λ₂, and so on. Similarly, a ring resonator 170-12 may be coupled to light propagating at λ₁ within the waveguide 160-2, a ring resonator 170-22 may be coupled to light propagating at λ₂ within the waveguide 160-2, and so on.

A receiver controller 175 controls the resonant frequency of each of the ring resonators 170. The controller 175 may configure each of the ring resonators 170 to have a nominal resonant frequency corresponding to any one of the channel wavelengths λ₁, λ₂, λ₃, and λ₄. That is, the resonant frequency of each of the N ring resonators 170-1Q, . . . , 170-NQ of ring resonator set 165-Q may be set to couple to a selected one of the N channel wavelengths, thereby selectively coupling one of N wavelength components in the optical waveguide 160 to that ring resonator 170. Typically, within a wavelength set 165, each of the channel wavelengths λ₁, λ₂, λ₃, and λ₄ is assigned to only one ring resonator of a ring resonator set 165-Q.

Each of the ring resonators 170 is paired with an optical-to-electrical transducer 300, referred to herein as a domain converter 300. FIG. 3 illustrates a detail view of a representative domain converter 300. Each domain converter 300 includes a waveguide section 310 and a photodiode 320. The waveguide section 310 is located proximate the associated ring resonator 170 such that light is coupled from the ring resonator 170 to the waveguide section 310. The photodiode 320 converts the coupled optical signal to a corresponding electrical signal for further processing, e.g. demodulation of the received data stream. Each of the domain converters 300 may be identified by the same suffix as its associated ring resonator 170. Thus, e.g. a domain converter 300-11 is associated with the ring resonator 170-11, a domain converter 300-21 is associated with the ring resonator 170-21, etc.

Returning to FIG. 1, the controllers 135 and 175 act in a coordinated manner to transmit data from a selected one of the NM ring resonators 130 to a selected one of the MN ring resonators 170. For example, if it is desired to transmit the data stream received by the ring resonator 130-21 to the ring resonator 170-22, the controller 135 may configure the ring resonator 130-21 to couple to the channel wavelength λ₂, thereby modulating the λ₂ carrier with a data stream. The wavelength demultiplexer 145 routes the λ₂ carrier to the output 155-2 (see FIG. 4A). The receiver controller 175 configures the ring resonator 170-22 to also couple to the channel wavelength λ₂. Then, the transducer 300-22 converts the optical signal to the electrical domain for processing. It will be apparent to those skilled in the art that the described principle may be used to transmit data received by any of the ring resonators 130 to any desired instance of the transducer 300 thereby implementing a general M×N opto-electrical switching network.

FIG. 1A schematically illustrates how the optical network 100 may optically provide data connections between N electrical devices 800-1, . . . , 800-N and M electrical devices 900-1, . . . , 900-M. Each electrical device 800-R is connected to electrically transmit M data streams to a corresponding M ring resonator set 125-R. Each electrical device 900-S is connected to electrically monitor N data streams from a corresponding N ring resonator set 165-S. For that reason, any individual electrical device 800-R is able to communicate a digital data stream to any individual electrical device 900-S via the optical network 100. That is, the N electrical devices 800-1 to 800-N may independently communicate, in parallel, with the M electrical devices 900-1 to 900-M via the optical network 100. As an example, the electrical devices 800-1 to 800-N may be N digital data processors of a data center, and the electrical devices 900-1 to 900-M may be M digital data storage devices of the data center. Then, the optical network 100 enables each of the N digital data processors to selectively route a separate digital data stream to each of the M digital data storage devices.

In other embodiments, the optical network 100 may provide such parallel digital data connections between a first set of N data devices and a second set of M data devices. In the first set, the N individual devices may include various types of conventional devices that output digital data streams. In the second set, the M individual devices may include various types of conventional devices that input digital data streams.

The above embodiments have been described with each of the ring resonators 130 being configured to couple to one of the same set of channel wavelengths, e.g. λ₁, λ₂, λ₃, and λ₄. In such embodiments it may be preferable that the wavelength demultiplexer 145 provide cyclic permutations of the input channel wavelengths to the outputs, as previously described in various embodiments. In some other embodiments, the set of wavelengths at which each ring resonator set 125 couples to optical carriers is not constrained to be the same as the set of wavelengths at which the others of the ring resonator sets 125. In such cases, the wavelength demultiplexer 145 need not provide cyclic permutations of the input wavelength channels at its outputs. In particular, some such embodiments may select the wavelengths such that no two channels with a same wavelength ever simultaneously propagate on a same waveguide.

In embodiments in which the controllers 135 and 175 are collocated, coordination of the operation of the controllers may be easily accomplished using a data path 180 to communicate, e.g. timing information and/or data conveying the data channels selected for communications. In embodiments in which the controllers 135 and 175 are physically remote, such as for long-haul communications, the data path 180 may communicate a selected data channel and/or channel scheduling data to coordinate operation of the controllers 135 and 175.

The optical components of the system 100 may be formed conventionally, e.g. as planar structures formed over a silicon substrate, e.g. a silicon wafer. A convenient platform on which to form the system 100 is a silicon-on-insulator (SOI) wafer, but embodiments of the invention are not limited thereto. For example, a dielectric layer, e.g. plasma oxide, could be formed on any suitable substrate, and a silicon layer could be formed thereover by any suitable method. Other embodiments may use a substrate formed from, e.g. glass, sapphire or a compound semiconductor. Those skilled in the pertinent art are familiar with such fabrication techniques.

In some embodiments optical and electrical components of the system 100 are formed on a same substrate. In such a system, e.g. silicon-based electronic components may be formed on one region of a photonic integrated circuit (PIC), and optical components may be formed on another region of the PIC. Interconnects may provide conductive paths from the domain converters 300 to the control stage 110.

In other embodiments, such as represented by FIGS. 5A-5C, portions of an opto-electronic system may be formed on separate substrates. FIG. 5A illustrates one such system 500, formed according to one embodiment. Electrical components are formed on an electrically active substrate 510, optical components are formed on an optical substrate 520, and interconnects are formed on an interconnect substrate 530. The substrates 510, 520 and 530 are then face-joined to form the operable system 500.

The electronic substrate 510 may include electronic components such as transistors, diodes, resistors and capacitors to implement electrical functions of the system 100. Such functions may include, but are not limited to, the functions of the controllers 135 and 175, including switching, signal conditioning and amplification. The electronic substrate 510 may include a base layer 540, e.g. a silicon wafer, and active layers 550 that include electronic devices and interconnects. The substrate 510 may be formed from any conventional and/or future-discovered processes, and is not limited to any particular material types. By way of example, without limitation, such materials may include silicon, silica, SiN, InP, GaAs, copper interconnects, aluminum interconnects, and/or various barrier materials.

The optical substrate 520 may include optical components of the transmit stage 105, the switching stage 110, and the receiver stage 115. Such components include, e.g. grating couplers, AWGs, optical waveguides, microcavity resonators, optical power splitters, optical power combiners, and photodiodes. The optical waveguides may be formed from planar or ridge structures by conventional and/or novel processes. Such components typically include an optical core region and an optical cladding region. The core regions may be formed from any conventional or nonconventional optical material system, e.g. silica, silicon, LiNbO₃, a compound semiconductor alloys such as GaAlAs, GaAlN or InP, or an electro-optic polymer. Some embodiments described herein are implemented in Si as a nonlimiting example. While embodiments within the scope of the invention are not limited to Si, this material provides some benefits relative to other material systems, e.g. relatively low cost and well-developed manufacturing infrastructure. The cladding region may include homogenous or heterogeneous dielectric materials, e.g. silica or benzocyclobutene (BCB). Some portions of the cladding region may include air, which for the purposes of this discussion includes vacuum.

The interconnect substrate 530 includes additional interconnect structures that may configure operation of the system 500. The interconnect substrate 530 may include any dielectric and conductive (e.g. metallic) materials needed to implement the desired connectivity. In some cases, formation of the substrate 530 may include the use of a handle wafer to provide mechanical support, after which the substrate 530 is removed from the handle.

The electronic substrate 510 may be joined to the interconnect substrate 530 by, e.g. a bump process or, as illustrated, a wafer bonding process. Such processes are well known to those skilled in semiconductor manufacturing, and may include, e.g. chemical mechanical polishing (CMP) to prepare the substrate surfaces for bonding. The interconnect substrate 530 may be joined to the optical substrate 520 by, e.g. a bump process as illustrated in FIG. 5A, or a wafer bonding process as illustrated in FIG. 5B. In the bump process, solder balls 560 join interconnect structures in the substrate 530 to metalized via structures 570 in the optical substrate 520. The via structures 570 may provide electrical and/or mechanical connectivity between substrates 520 and 530.

FIG. 5C illustrates another embodiment of the system 100 in which the interconnections and optical functions are combined into an integrated substrate 580. In the illustrated embodiment the substrate 580 includes the optical substrate 520 and interconnect layers 530a and 530b formed on either side of the optical substrate 520. The integrated substrate 580 may then be joined to the substrate 510 by, e.g. wafer bonding.

The separate formation of the electronic substrate 510, the interconnect substrate 530 and the optical substrate 520 may serve at least one of several purposes. First, the thermal budget required to form some features, e.g. high quality waveguides in the optical substrate 520, may be incompatible with other features, such as doping profiles of transistors in the electrically active substrate 510. Second, the substrates 510, 520 and 530 may be formed separately by entities with specialized skills and/or fabrication facilities and joined by another entity. Third, where security is desired regarding the function of the assembled system 500, the fabrication operations may be assigned to the various entities such that no one entity acquires sufficient knowledge to determine the specific functionality of the device. The final assembly may then be completed under secure conditions to ensure confidentiality of the operation of the assembled system 500.

Turning to FIG. 6, a method 600 is provided for, e.g. forming the system 100 according to various embodiments. The steps of the method 600 are described without limitation by reference to elements previously described herein, e.g. in FIGS. 1-5. The steps of the method 600 may be performed in another order than the illustrated order, and in some embodiments may be omitted altogether and/or performed concurrently or in parallel groups. This method 600 is illustrated without limitation with the steps thereof being performed in serial fashion, such as by separate processing on different substrates. Other embodiments, e.g. those utilizing a common multiple substrate, may perform the steps partially or completely in parallel, and in any order.

In a step 610, an input waveguide, e.g. the waveguide 120-1, is formed and optically connected to a wavelength demultiplexer, e.g. the wavelength demultiplexer 145. In a step 620 microcavity resonators of a first input set of microcavity resonators are formed. These resonators are located adjacent the input waveguide such that each microcavity resonator is configured to controllably couple to a corresponding one of a plurality of frequency channels propagating within the input waveguide.

Some embodiments of the method 600 include a step 630, in which a plurality of output waveguides is formed. Each waveguide is optically connected to the wavelength demultiplexer. The wavelength demultiplexer is configured to route each carrier signal to a corresponding one of the output waveguides.

Some such embodiments include a step 640, in which a plurality of output microcavity resonator sets is formed. Each resonator set includes a corresponding plurality of microcavity resonators. Each microcavity resonator of each output set is located adjacent a same corresponding one of the output waveguides such that the microcavity resonators of each set may controllably couple to a corresponding different wavelength channel propagating within the corresponding output waveguide.

FIG. 7 presents a method 700, e.g. of forming the system 100. The steps of the method 700 are described without limitation by reference to elements previously described herein, e.g. in FIGS. 1-5. The steps of the method 700 may be performed in another order than the illustrated order, and in some embodiments may be omitted altogether and/or performed in parallel or in parallel groups. Herein and in the claims, “provided” or “providing” means that a device, substrate, structural element, etc., may be manufactured by the individual or business entity performing the disclosed method, or obtained thereby from a source other than the individual or entity, including another individual or business entity.

The method includes a step 710, in which a first substrate is provided. The substrate has an input waveguide optically connected to a wavelength demultiplexer. A first input microcavity resonator set including a plurality of microcavity resonators is located adjacent the input waveguide.

In a step 720 a second substrate is provided. The second substrate has an electronic controller formed thereover. The controller is configured to control the microcavity resonators to controllably couple each to a corresponding one of a plurality of frequency channels of an optical signal propagating within the input waveguide.

In a step 730 the first and second substrates are joined, thereby connecting the controller to the microcavity resonators.

Those skilled in the art to which this application relates will appreciate that other and further additions, deletions, substitutions and modifications may be made to the described embodiments. 

What is claimed is:
 1. A system comprising: a first plurality of separate sets of optical ring resonators; a second plurality of separate sets of optical ring resonators; and an optical multiplexer/demultiplexer having a set of optical inputs and a set of optical outputs; and wherein: each set of the first plurality of separate sets is optically connected to a corresponding one of the optical inputs of the optical multiplexer/demultiplexer; and each set of the second plurality of separate sets is optically connected to a corresponding one of the optical outputs of the optical multiplexer/demultiplexer.
 2. The system of claim 1, further comprising a plurality of first devices, each first device being connected to modulate digital data streams onto optical carriers via the ring resonators of a corresponding one of the sets of the first plurality.
 3. The system of claim 2, further comprising a plurality of first apparatuses, each first apparatus being connected to demodulate digital data streams from optical carriers via the ring resonators of a corresponding one of the sets of the second plurality.
 4. The system of claim 1, further comprising a plurality of first apparatuses, each first apparatus being connected to demodulate digital data streams from optical carriers via the ring resonators of a corresponding one of the sets of the second plurality.
 5. The system of claim 1, further comprising an electronic controller capable of separately adjusting resonant frequencies of some of the ring resonators of the sets of the first plurality.
 6. The system of claim 1, wherein the electronic controller is capable of separately adjusting resonant frequencies of some of the ring resonators of the sets of the second plurality.
 7. The system of claim 1, further comprising: a plurality of first optical fibers, each first optical fiber connecting a corresponding one of the sets of the first plurality to a multi-wavelength channel optical source.
 8. The system of claim 7, wherein each first optical fiber connects to a corresponding one of the optical inputs of the optical multiplexer/demultiplexer.
 9. A system, comprising: an input waveguide optically connected to an input of an optical demultiplexer; and a first microcavity resonator set including a plurality of microcavity resonators located adjacent said input waveguide such that each microcavity resonator is able to couple to a corresponding one of a plurality of wavelength channels of an optical signal propagating within said input waveguide.
 10. The system of claim 9, further comprising a plurality of output waveguides, each output waveguide being optically connected to a corresponding optical output of said wavelength demultiplexer.
 11. The system of claim 10, further comprising a plurality of output microcavity resonator sets each including a corresponding plurality of microcavity resonators, each microcavity resonator set being optically coupled to a corresponding one of said output waveguides, the microcavity resonators of each output set being able to separately couple to wavelength channels of an optical signal propagating within said corresponding one of the output waveguides.
 12. The system of claim 11, further comprising a plurality of optoelectric transducers, each of said transducers being optically coupled to convert an optical signal within a corresponding one of said output microcavity resonators to an electrical signal.
 13. The system of claim 9, wherein said wavelength demultiplexer comprises an arrayed waveguide grating.
 14. The system of claim 9, further comprising control electronics configured to control a resonant frequency of said microcavity resonators.
 15. The system of claim 9, wherein said wavelength demultiplexer is a wavelength-cyclic optical demultiplexer.
 16. The system of claim 9, wherein said each microcavity resonator of said plurality of microcavity resonators is a ring resonator.
 17. A method comprising: providing an input waveguide optically connected to a wavelength demultiplexer; and providing a first input microcavity resonator set including a plurality of microcavity resonators located adjacent said input waveguide such that each microcavity resonator is able to couple to a corresponding one of a plurality of wavelength channels propagating within said input waveguide.
 18. The method of claim 17, further comprising providing a plurality of output waveguides optically connected to said wavelength demultiplexer.
 19. The method of claim 18, further comprising providing a plurality of output microcavity resonator sets each including a corresponding plurality of microcavity resonators, each microcavity resonator set being optically coupled to a corresponding one of said output waveguides.
 20. The method of claim 19, further comprising providing a plurality of optoelectric transducers, each of said transducers being optically coupled to a corresponding one of said microcavity resonators.
 21. The method of claim 17, wherein said wavelength demultiplexer comprises an arrayed waveguide grating.
 22. The method of claim 17, further comprising providing control electronics configured to modulate a resonant frequency of some of said microcavity resonators.
 23. The method of claim 17, wherein said microcavity resonators are ring resonators.
 24. A method, comprising: providing a first substrate having an input waveguide optically connected to a wavelength demultiplexer, and a first input microcavity resonator set including a plurality of microcavity resonators located adjacent said input waveguide, each of said microcavity resonators being configured to couple to a different frequency of an optical signal propagating within the input waveguide; providing a second substrate having an electronic controller formed thereover, said controller configured to control said microcavity resonators to controllably couple to a corresponding one of the frequency channels; and joining said first and second substrates thereby connecting said controller to said microcavity resonators. 